One of the most frequent recommendations in medicine is to carry out physical exercise in a moderate way due to the beneficial effects that it has on the body.
The athlete’s diet must consider the individual nutritional needs of fuel and structural material, as well as regulatory elements based on age, sex and the type of physical activity carried out.
Among the oldest myths related to the nutrition of athletes, is that of consubstantiality, according to which the ingestion of large amounts of foods rich in protein was recommended in order to replace the muscle mass, which was supposedly consumed during exercise. Another nutritional myth is the massive consumption of pills, powders and potions rich in vitamins, to enhance the efficiency in obtaining energy by the body from food.
Some common mistakes among athletes are low food intake before a competition, in order to reach a certain weight, or excessive food consumption, to ensure a greater reserve of fuel for exercise. Another common mistake is the ingestion of hyperosmotic solutions with electrolytes or sugars that, instead of favoring rehydration, lead to a reduction in water reserves.
Pre-exercise diet
In sports with a predominance of aerobic work, glucose and glycogen are essential for muscle metabolism when an exercise is carried out with a moderate to strong intensity and lasts for more than 75-90 minutes. That is why it is important to instill in the athlete the idea that a diet with fewer carbohydrates than is advisable can be the origin of early fatigue; because when it comes to aerobic endurance exercise, fatigue generally appears as a consequence of muscle glycogen depletion or hypoglycemia.
Some days before a basically aerobic competition, such as a marathon or a triathlon, it is advisable for the athlete to regulate his diet and training in an attempt to maximize (“overcompensate”) glycogen stores. A practical method to achieve this consists of putting into practice a tapering, that is, a modification of the training, in such a way that in the seven days prior to the competition the volume is significantly decreased, in a progressive way, maintaining a high training intensity . During days –7, -6, -5 and –4 a low carbohydrate diet is followed. This will make the muscle partially depleted of its glycogen stores and ready to overcompensate. During the three days prior to the competition, the diet must be rich in carbohydrates,
However, ingesting this amount of food can be accompanied in some people by minor gastrointestinal symptoms such as feelings of fullness and discomfort. For this reason, studies carried out by Lamb and Snyder 1 (1991) advise substituting part of these complex carbohydrates for drinks rich in maltodextrin, low in residues and very energetic, as a method as effective as the diets commonly used to “recharge” the muscle.
The precompetitive meal, a carbohydrate-rich meal taken in the hours leading up to competition, can replenish liver and muscle glycogen stores. The liver, in charge of maintaining plasma glucose levels, requires frequent meals to conserve its small glycogen reserve. Those athletes who follow a fast in the previous 6-12 hours, and do not consume carbohydrates during the competition are more likely to develop hypoglycemia during the competition.
A meal that mixes fast, intermediate and slow assimilation carbohydrates is preferable. In the previous hour it is highly recommended that all food be in liquid form.
The recommendations made by different committees of experts in nutrition about the daily protein needs of a person are in a range that oscillate between 0.8 and 1.2 g / kg / d, but it is not resolved if these recommendations are sufficient for an athlete. For Butterfield and Calloway2 (1984), these amounts are sufficient for people who perform low intensity aerobic physical activity, such as walking; however, athletes who usually work with higher intensities need more protein in their diet.
In most cases, you can get enough protein from your daily diet. However, in some circumstances the use of protein supplements may be advantageous, especially because they contain very little fat, purines or cholesterol.
On the one hand, resistance exercise can produce a considerable glycogenolytic effect. And a significant reduction in muscle glycogen concentration has been seen to be associated with fatigue and decreased strength. There are also studies suggesting that carbohydrate intake immediately before and during such an exercise can improve physical performance, can accelerate muscle glycogen recovery after resistance exercise, and can optimize protein synthesis and muscle hypertrophy.
Most sports dietitians maintain that it is not necessary to supplement the diet with proteins and / or amino acids, and that an adequate calorie diet, which provides 15% of these in the form of protein, is sufficient to meet the athlete’s needs.
1 Lamb DR, Zinder Ac. “Muscle glycogen loading with a liquid carbohydrate supplement.” Int J Sport Nutr 1991; 1: 52-60
2 Butterfield GE and Calloway DH. “Physical activity improves protein utilization”. Brt J Nutr 1984; 51: 171-84.
Food during physical exercise
Holloszy and Kohrt3 (1996) point out that it is possible to cover long distances working at a high average intensity, without depleting the muscular reserves of glycogen, taking a supplement of carbohydrates of rapid assimilation, regardless of whether they are taken in solid or liquid form. During short periods of rest, or during periods when exercise intensity drops sufficiently, rapid synthesis of a certain amount of glycogen can occur in muscle fibers with a low glycogen concentration and not active in that type of exercise.
3 Holloszy JO, Kohrt WM. “Regulation of carbohydrate and fat metabolism during and after exercise”. Annu Rev Nutr 1996; 16: 121-38.
Post-exercise diet
The rapid recovery of glycogen stores after a training session or competition is essential if you want to maintain optimal performance in successive training sessions or in competitions closely followed. However, the speed with which the muscle can recover its glycogen stores will be closely related to three dietary factors: the time elapsed between the end of physical exercise and the start of carbohydrate consumption, the type of carbohydrate chosen and the amount ingested.
Some studies compiled by Friedman et al.4 (1991) estimate that administering a carbohydrate supplement every two hours, taking the first dose in the first 15 minutes after finishing the exercise, optimizes the rate of glycogen resynthesis. In addition, the intake of a supplement that mixes carbohydrates and proteins is accompanied by a faster recovery of glycogen stores because it promotes higher levels of insulin in plasma.
On the other hand, Lamb et al. 5 (1990) provide data that support the existence of a limit in the intake of these carbohydrates, with a range that would oscillate between 500 and 600 g / d, above which no increased glycogen storage or improved physical performance.
In short, from a practical point of view, after a physical exercise, that athlete should immediately start drinking between 1.5 to 2 liters of water in which, for example, 50-70 grams of glucose or maltodextrin have been dissolved. /liter. Between 1.5 and 2 hours later, you should have a meal that contains, for example a cold salad with rice, or cooked potato, or peas. Also, a dish that combines meat and rice or mashed potatoes. It is also advisable to include foods such as fruit yogurt, rice pudding, banana, fruit juices, raisins; and the energy drink with the carbohydrate concentration already described, which will have to continue consuming during the following hours until completing a total of 500 to 600 grams of carbohydrates.
However, Coyle6 (1992) points out that when for various reasons a person cannot eat and / or drink carbohydrates frequently (every two hours), the last meal should provide the amount of carbohydrates equivalent to the period of time that they will be without feeding. Costill et al. 7 (1981) find that glycogen synthesis is similar when two large meals are eaten compared to seven smaller meals. However, if a person decides to eat only twice a day, they have to be aware that each of them will contain a large amount of food if they eat only foods such as legumes, potatoes, rice, pasta, cereals, etc. Therefore, in this case it is necessary to drink solutions with carbohydrate concentrates
